Constrained networks include, for example, Low power and Lossy Networks (LLNs), such as sensor networks. These constrained networks have a myriad of applications, such as Smart Grid, Smart Cities, home and building automation, etc. Various challenges are presented with LLNs, such as lossy links, low bandwidth, battery operation, low memory and/or processing capability, etc. Large-scale internet protocol (IP) smart object networks pose a number of technical challenges. For instance, the degree of density of such networks (such as Smart Grid networks with a large number of sensors and actuators, smart cities, or advanced metering infrastructure (AMI) networks) may be extremely high. For example, it is not rare for each node to see several hundreds of neighbors. This architecture is particularly problematic for LLNs, where constrained links can wreak havoc on data transmission.
Network deployments utilize a number of different interface technologies, including RF, Powerline Communications (PLC), and cellular. Each interface technology provides its own set of strengths and weaknesses. LLNs communicate over a physical medium that is strongly affected by environmental conditions that change over time. Some examples include temporal changes in interference (for example, other wireless networks or electrical appliances), physical obstruction (for example, doors opening/closing or seasonal changes in foliage density of trees), and propagation characteristics of the physical media (for example, temperature or humidity changes). PLC link technologies, for example, are known to experience significant unpredictable noise that depends on the quality of the electric lines and the kinds of electric devices attached to the network.
Low-cost and low-power designs limit the capabilities of the transceiver. In particular, LLN transceivers typically provide low throughput. Furthermore, LLN transceivers typically support limited link margin, making the effects of interference and environmental changes visible to link and network protocols. Interference may be external (for example, non-network devices generating electromagnetic interference) or internal (for example, other network devices communicating within the same frequency band).
Interface technologies common to LLN deployments (RF and PLC) communicate on shared media. For this reason, communication between different pairs of devices within physical proximity may interfere with each other and is often called self-interference. Note that self-interference can occur in multiple ways in multichannel systems. In one case, two devices transmitting on the same channel simultaneously may cause a collision at the receiver. In another case, because typical interface technologies are half-duplex, a device cannot transmit and receive at the same time even when communication occurs on different channels. As a result, self-interference can occur even when communicating multiple packets along a single path. For example, in a path A→B→C, A cannot forward a packet to B while B is forwarding a packet to C.
Network users would like to have endpoints of the network determine the interface options for all devices on a transmission path and then select interface options for each device to minimize self-interference. Current technologies do not provide the ability to devise a source route for a transmission that will minimize self-interference with network devices.